1. Field of the Invention
The present invention is directed to a hold-down device for a fuel injection device.
2. Description of Related Art
Published German patent application document DE 29 26 490 A1 already describes a fastening device for fastening a fuel injector to an intake manifold, in which the fuel injector is axially fixed to the fuel distributor line or to a plug nipple via a fastening element designed in the form of a U-shaped securing bracket which is provided with two legs that are flexible in the radial direction. In the assembled state, the securing bracket engages through corresponding openings in the plug nipple, and is capable of snapping into a recess, designed as an annular groove, in a connecting fitting of the fuel injector. The axial play between the recesses and the securing bracket, as well as between the annular groove and the securing bracket, should be kept small in order to achieve a precise fixing of the fuel injector without stressing the seal.
A disadvantage of the fastening device known from published German patent application document DE 29 26 490 A1 is in particular the stressing effect of the various holding parts on the fuel injector. The flow of force that is produced in the fuel injector results in deformations, and thus in changes in the lift of the valve needle, up to the point of jamming, and to a compressive or flexing load on the housing parts, which in general have thin walls and are welded to one another at various points. In addition, each fastening measure, using for example a bearing collar, results in an increase in the radial extension of the fuel injector, and thus in an increased space requirement during installation.
Published German patent application document DE 101 08 193 A1 describes a fastening device for the mutual fastening of a fuel injector in a cylinder head of an internal combustion engine, and of the fuel injector to a fuel distributor line. The fastening device has a sleeve that is clamped between a shoulder of the fuel distributor line and a shoulder of the fuel injector and is made of an elastic material. Due to its tubular structure, the sleeve may transmit the hold-down forces to the fuel injector with only limited effectiveness. The surfaces, loaded by the shoulders of the fuel injector and the fuel distributor line, of the sleeve used as the hold-down device represent the cut edges that result from the process of manufacturing the sleeve blank.
Various designs of hold-down devices are also known from published German patent application document DE 10 2004 048 401 A1, to which reference is made for better understanding of the present invention based on FIGS. 1 through 3 below.